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This is the Griffith Observatory Sky Report through December 30, 2015. Here’s what’s happening in the skies of southern California.
The phase of the moon changes from waxing gibbous to full on the morning of the 25th. This will be the first full moon that happens on Christmas since 1977, and the next, in the Pacific Time zone, will be in 2034. Because it occurs near the start of winter, December’s full moon has the traditional nick name, Long Nights Moon. The moon is waning gibbous on the remainder of the nights through the 30th. Between the 23rd and 30th, the time of moonrise advances an average of 57 minutes per night, and changes from 3:43 p.m. to 10:19 p.m.
The brilliant planet Jupiter, in the constellation Leo the Lion, rises over the eastern horizon before 11:40 p.m. and is due south at about 5:00 a.m. Binoculars can reveal Jupiter’s four largest moons, and you can use a telescope to see the banded structure of Jupiter’s clouds.
The brightest planet, Venus, rises in the east at about 4:00 a.m., and is 30 degrees high in the east-southeast at dawn. A telescope is needed to see the gibbous phase of Venus.
The orange planet Mars is between Jupiter and Venus in the constellation Virgo the Maiden. It also appears 5½ degrees to the left of Virgo’s brightest star, Spica. As dawn starts, Mars is about 43 degrees high in the east-southeast. From Los Angeles, this elevation is the highest that the planet will appear above the horizon as seen from Los Angeles for the next two years. Mars is still on the far side of the sun, making it a distant and tiny telescopic target, but starting on the 27th, observers in Los Angeles have a chance to look for the planet’s most recognizable dark feature, triangular Syrtis Major, a shield volcano on Mars.
Golden planet Saturn, in the constellation Ophiuchus the Serpent Bearer, can be seen to the lower left of Venus starting at 6:00 a.m. Saturn will appear higher at that time on each successive morning, ascending from 8 degrees on the 24th to 12 degrees on the 30th.
The International Space Station will pass high over Los Angeles on the evening of Wednesday the 23rd. The ISS will first appear above the northwest horizon at 5:56 p.m. It will be nearly overhead at 5:59 p.m. and will visible until 6:02 p.m. as it approaches the southeast horizon.
Comet Catalina, C/2013 US10, has to compete with bright moonlight to be seen through binoculars this week. The comet is about 45 degrees above the east-southeast horizon at dawn, and is in the vicinity of the bright orange star Arcturus of the constellation Boötes the Herdsman. The comet appears to the lower right of the star, moving closer to it from an angular distance of 12 degrees on the 24th to only 3 degrees on the 30th. The comet should be bright enough to see through binoculars and small telescopes. A finder map is available from Sky and Telescope.
Free views of the sun during the day and of the moon, planets, and other celestial objects at night are normally available to the public in clear weather through Griffith Observatory’s telescopes from Tuesday through Sunday before 9:30 p.m. This week, however, the Observatory will close at 5:00 p.m. on Thursday, December 24, and will not be open at all on Friday, December 25. Check our website for the schedule. The next public star party on the grounds of Griffith Observatory, hosted by the Los Angeles Astronomical Society, the Sidewalk Astronomers, and the Planetary Society, will take place on Saturday, January 16, 2016.
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From Griffith Observatory, I’m Anthony Cook and I can be reached at griffithobserver@gmail.com